It is not like Patanjali medicines are better than other. Some of them are (for example I personally use their toothpaste). It is more about cult system and current socio-political environment in India.
These days, in India, 'hindu nationalism' along with 'anti-Congress' movement is on the rise. And Ramdev has projected himself as an ultimate ambassador of everything Hinduism or Hindu-Nationalism has to offer (Yoga, Ayurvedic medicines, Made in India products, true ascetic life, spirituality etc etc).
The right-wing central government and rise of Ramdev are not two separate phenomena. They are closely entwined. And they both support each other. As things stand now, no political party can dare to touch Ramdev. He has too much clout because of his countless followers. Even his traditional political opponents don't want to mess with him.
His business is probably far bigger than described in many news articles. We don't have financial numbers. His tax filings have been shady and noone can question him. He's bought may be thousands of acres of lands from government at 75-80% discount so that he can 'promote yoga and ayurveda'. I also read somewhere he actually bought an island somewhere in Europe though not sure about it.
Even a small town with population less than 15000 has at least half dozen shops which sells only Patanjali products. No other FMCG company has this much clout.
This is all about cult following and current rise of hindu nationalism in india. Better ayurvedic medicines and Yoga teachers have always been around. But Ramdev was there at the right time (widespread use of SM, anti-Congress sentiments), did all the right things, projected himself as an ultimate 'patriotic and honest hindu yoga guru' effectively.
Now he is selling noodles, chocolates and cosmetic products in the name of patriotism and spirituality.